Variable conductor of high negative temperature co-efficient



Aug. 25, 1931. ANDRE 1,820,591

VARIABLE CONDUCTOR OF HIGH NEGATIVE TEMPERATURE (JO-EFFICIENT Filed Sept. 27, 1927 INVENTOR Henri ndre W atented Aug. 25,

UNITED STATES PATENT OFFICE HENRI ANDRE, or PARIS, FRANCE VARIABLE CONDUCTOR OF HIGH NEGATIVE TEMPERATURE (lo-EFFICIENT Application filed September-27, 1927, SeriaLNo. 222,406, and in France November 17, 1928. A

This invention relates to conductors having high negative temperature coeflicient and automatic variable resistance, and methods for producing the same.

The object of this invention, more particularly, is to provide an electrically conductive element having, in addition to the characteristics described above, and more definitely, though not in limitation, a resistance range from infinity to zero through a temperature range of 0 C.100 (1., said element being capable of cooling rapidly.

The element is adapted for use in rheostats, thermostats and current regulating devices.

The invention comprises, broadly, silver compounded with a more fusible metalloid, such as sulphur or phosphorus.

The element may be made by adding to powdered silver an excess of sulphur and heating the mixture to a temperature over 800 C., whereat the mass fuses and may be cast to give it the desired form.

Where the element is to be employed in a device of slow action, it will have a large area of radiation surface; 1f 1t is to be used in a quick action device, it will have little radia-.

tion surface, it being obvious, in these cases, that the quicker the temperature of the element is raised to its operative limit, the greater will be the flow of current and the faster the response. If it is desired to raise the temperature of the element still more quickly, it may be covered with heat insulating material.

The rapidity of action of the device may be controlled, of course, in addition, by varying the dimensions of the element, such as its length and diameter in conformity with the electric power to be dissipated. If the power to be dissipated is relatively large and should be so treated under high tension then the conductor will be long and thin. If on the contrary, the power to be dissipated is relatively small and should be so treated under low pressure, then the conductor will be short and thick.

In explanation of the chemistry involved in the formation of the element, it may be said that the sulphur and the silver do not seemingly enter into chemical combination to form silver sulphide, but rather a solid ment, and under these conditions it is not necessary to coat the element with the sulphur as aforesaid. However, in this case, should the element be subjected to a temperature in excess of 100 (1., it shouldbe coated with molten sulphur.

- The connections of the conductor to the external circuit must be ensured by the medium of silver contacts, because when using other substances thansilver it might happen that the resistance of the circuit be not the same for the different polarities applied at one terminal of theconductor.

The accompanying drawing illustrates by way of example a cross-section of a resistance element constructed in accordance with the invention.

The mass 1 is a solid mixture of sulphur and colloid silver, the silver having been fused or alloyed with the sulphur. The dimensions and form of said mass 1 will be determined by the use to which the resistance element is to be adapted in accordance with th considerations previously set forth. A coating 2 of sulphur surrounds said mass 1 and is maintained in proper position by a casing 3.

A plurality of metallic rods 4 pass through mass 1 and easing 3 as shown to maintain said mass in vertical spaced relation to said casing 3. Knurled thumb nuts 5 are threaded on said rods 4 to secure the same with respect to the casing 3.' A plurality of washers 6 encircle said rods 4 on either side of the mass 1 and a plurality of helical springs 7 also encircle said rods 4 and abut said washers and the casing 3, thus maintaining a laterallv 2 I Lemuel spaced relation between the mass 1 and casing)3.

f course without de arting from the spirit of the invention ot er methods may be 7 f ima 'ned for the manufacture of the special con uctor, as well as various other applications than those given by way of example.

Having described my invention, what I claim is:

10 1. Variable-resistance conducting material having a high negative temperature coefiicient comprising silver and a more fusible metalloid in quantity greater than that which is necessary to'bind all of said silver and in a manner to form a saturated combination of said silver and said metalloid.

2. Variable-resistance conducting material having a high negative temperature coefficient, comprlsing silver and sulphur in quantity larger than that necessary to form silver sulghide with the total quantity of silver use 3. Variable-resistance conducting material having a high negative temperaturecoeflicient, comprising silver and sulphur in quantity greater than that required to form silver sulphide with the total quantity of silver used, a layer of fused sulphur surrounding the solid part of the substance.

4. Variable-resistance conductor substance having a high negative temperature coefiicient, comprising sllver and sulphur in quantity reater than that required to form silver sulphide with the total quantity of silver '35 used, a layer of fused sulphur held by an outer envelope surrounding the solid part of the substance.

' HENRI ANDRE. 

